You may view the sun—and thus the planet Venus passing in front of the sun—only if you use proper solar filters or indirect viewing techniques.  See http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/safety2.html for details, including links for purchasing solar viewing aids.  For an overview of the techniques listed below, see our Safe Viewing Techniques page.  

The preferred method is to view a magnified image of the sun through a telescope that has a solar filter on the large end.  Do  not look through a telescope without a solar filter on the large end.  And never use small  solar filters that attach to the eyepiece (as found in some older, cheaper telescopes).

You can project the image with binoculars, but  do  not look through binoculars unless you have proper solar filters on the large ends.  You can also make a clever device that will project onto a viewing screen the image of the sun.  Because the dot of Venus will be small relative to the sun, pinhole projection techniques—suitable for tracking eclipses—are ineffective for witnessing and timing the transit of Venus.

While it has been suggested that you can use #14 welder’s glasses or darker, do not view through welding glasses that transmit more light.  Do not consider the numbers to be additive; for example, do not use two #7 welding glasses on top of each other to make a #14.

For many observers in the North America, the transit begins near sunset on June 5, 2012.   Do not be lulled into thinking the sun’s intensity is significantly diminished when it is low on the horizon.  Severe eye damage or blindness can result if you view the sun without proper eye protection.

See our Safe Viewing Techniques page for more information.